I have a bit of experience diving some of the places that people on this topic have considered dangerous. My comments:
PNG
I have been to PNG five times. I have stayed in the capital Port Moresby for 2 weeks. I have never felt threatened, although like many USA cities, you need to use some common sense. Yes, caution does need to be used in PM (and a couple of other cities), but generally it is very safe. Yes, there are walled communities, but I saw more in the USA than I have seen in Australia or UK (never seen one in either) or PNG.
Solomon Islands
I have been to SI four times. Apart from when there was a problem back in the early 2000s, the whole country is pretty safe. Even when there was a problem, most of the attention was to other SI racial groups rather than visiting westerners.
Chuuk Lagoon
I have been there six times. I have never had a problem or felt threatened. I have walked around the island a lot, including at night. Unless things have changed in the past five years, then this is a safe place.
Indonesia
To dive, most people go to Bali (or pass through it). Yes, Bali had two bombings in the 2000s, most of the victims were Australian. However, Bali is still the second most popular travel destination for Aussies (after New Zealand). I have been there twice, never a problem. As divers, you are very, very, unlikely to have any terrorism problem unless you spend all your time in the area close to Denpasar and there was another terrorism threat. The diving is not in this area.
I think that some nationalities are more prone to being worried about things like this. Australians seem to be a bit more capable of working this out, or else we are brave or stupider than others!
